The speaker says they are inventing their own life as they go, and they call it "a cheap miracle." It's a funny, modest phrase: the act is wondrous, but nothing about it is grand or expensive. Then comes the image of a playhouse full of "proper citizens," as if ordinary respectable life were a kind of theatre, and the speaker is both the cast and the committee running it.
The list of roles that follows moves from small to strange. A child wasting an hour, someone playing to forget growing old, a Christ hiding under the table, and finally a madman in a nightgown dancing in the street. The repeated "I play" has a double meaning: acting and simply playing, like a kid.
The mood is light but a little uneasy. The speaker seems to feel that identity is made up, and fear of aging sits underneath. Still, the ending is joyful and free. Dancing in public, ignoring what the citizens think, feels like the poem's answer.